spi_bitbang: short transfer status fix

SPI controller drivers return number of bytes actually transfered from
bitbang->txrx_bufs() method.  This updates handling of short transfers (where
the transfer size is less than requested):

 - Even zero byte short transfers should report errors;
 - Include short transfers in the total of transferred bytes;
 - Use EREMOTEIO (like USB) not EMSGSIZE to report short transfers

Short transfers don't normally mean invalid message sizes, but if the
underlying controller driver needs to use EMSGSIZE it can still do so.

[db: fix two more minor issues]
Signed-off-by: Jan Nikitenko <jan.nikitenko@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index f7f8580edad86c9be126ce1b6abd97d7629ee261..71e881419cddaa6ba9c77f588ae6723ff633249a 100644 (file)
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -344,12 +344,14 @@ static void bitbang_work(struct work_struct *work)
                                        t->rx_dma = t->tx_dma = 0;
                                status = bitbang->txrx_bufs(spi, t);
                        }
+                       if (status > 0)
+                               m->actual_length += status;
                        if (status != t->len) {
-                               if (status > 0)
-                                       status = -EMSGSIZE;
+                               /* always report some kind of error */
+                               if (status >= 0)
+                                       status = -EREMOTEIO;
                                break;
                        }
-                       m->actual_length += status;
                        status = 0;
 
                        /* protocol tweaks before next transfer */